<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    *{
      box-sizing: border-box;
      margin: 0;
      padding: 0;
    }
    #container {
      width: 500px;
      height: 500px;
      background: green;
    }
    .left {
      width: 100%;
      height: 0.5px;
      /* transform: scale(0.5,0.5); */
      margin-top: 100px;
      background: red;
    }

    .right {
      float: left;
      width: 100px;
      height: 100px;
      background: blue;
    }
  </style>
</head>
<body>
  <!-- <div id="container" class="clearfix"> -->
    <p class="left"></p>
    <!-- <div class="r"> -->
      <!-- <p class="right">我是右边</p> -->
    <!-- </div> -->
    
  <!-- </div> -->
  <script>
  </script>
</body>
</html>